A novel Si-based detector, having a low noise and a high sensitivity, up to a single photon detection, was used for a
biosensor application. It is a Silicon photomultiplier (SiPM), a device formed by avalanche diodes operating in Geiger
mode, in parallel connections. Arrays with different dimensions were electro-optically characterized (5×5; 10×10 and
20×20 pixels) in order to identify the best geometry to be used in terms of signal-to-noise ratio, for our purposes. The
SiPM array was used to study both traditional and innovative fluorophores. CY5 was chosen as “reference” marker. It
has an absorption peak at 649 nm and an emission peak at 670 nm. Ru(bpy)3[Cl]2 was identified as innovative fluorophore, since it has absorption and emission peaks at 455 and 630 nm, respectively. Measurements were carried out in both functional regimes: continuous and pulsed. Emission spectra in the range 550–750 nm were measured with both traditional photomultipliers tubes (PMT) and SiPM operating at room temperature in continuous mode. More
interestingly, fluorophore lifetimes were monitored showing that SiPM can measure lifetimes as short at 1 ns (CY5
lifetime), well below the lowest PMT limit (23 ns). Ru(bpy)3[Cl]2 lifetime characterization was performed with both
PMT and SiPM (being in the hundreds of ns range), as a function of the solvent and after deposition and drying on glass
We report on the design and the electro-optical characterization of a novel class of 4H-SiC vertical Schottky UV
detectors, based on the pinch-off surface effect and obtained employing Ni2Si interdigitated strips. We have measured, in
dark conditions, the forward and reverse I–V characteristics as a function of the temperature and the C–V characteristics.
Responsivity measurements of the devices, as a function of the wavelength (in the 200 – 400 nm range), of the package
temperature and of the applied reverse bias are reported. We compared devices featured by different strip pitch size, and
found that the 10 μm device pitch exhibits the best results, being the best compromise in terms of full depletion and
space-strip width ratio.
Functional Near Infrared Spectroscopy (fNIRS) uses near infrared sources and detectors to measure changes in
absorption due to neurovascular dynamics in response to brain activation. The use of Silicon Photomultipliers (SiPMs) in
a fNIRS system has been estimated potentially able to increase the spatial resolution. Dedicated SiPM sensors have been
designed and fabricated by using an optimized process. Electrical and optical characterizations are presented. The design
and implementation of a portable fNIRS embedded system, hosting up to 64 IR-LED sources and 128 SiPM sensors, has
been carried out. The system has been based on a scalable architecture whose elementary leaf is a flexible board with 16
SiPMs and 4 couples of LEDs each operating at two wavelengths. An ARM based microcontroller has been joined with a
multiplexing interface, able to control power supply for the LEDs and collect data from the SiPMs in a time-sharing
fashion and with configurable temporal slots. The system will be validated by using a phantom made by materials of
different scattering and absorption indices layered to mimic a human head. A preliminary characterization of the optical
properties of the single material composing the phantom has been performed using the SiPM in the diffuse radial
reflectance measurement technique. The first obtained results confirm the high sensitivity of such kind of detector in the
detection of weak light signal even at large distance between the light source and the detector.
The Silicon Photomultiplier (SiPM) is a novel pixelated photon detector able to detect single photon arrival with good timing resolution and high gain. In this work we present a complete study of the performances of different SiPMs produced by STMicroelectronics. Their potentialities and limits were identified using experimental measurements and electrical simulations performed both on single pixel and SiPM having up to ∼4000 pixels. SiPM was tested in different experiments such as photoluminescence emission measurement, lifetime measurement of semiconductor materials and light diffusion in highly scattering material in the near infrared spectrum showing its aptitude to replace PMT in those applications.
Silicon Photomultipliers (SiPMs) are fabricated in two different configurations: p-on-n and n-on-p junctions. More particularly p-on-n SiPMs turn out to be more suitable in nuclear medical imaging applications like Positron Emission Tomography (PET), due to their higher sensitivity in blue wavelength range where common PET scintillators have their emission spectrum. Here we report on the preliminary results of the electro-optical characterization performed on the first STMicroelectronics p-on-n SiPMs with standard (45%) and enhanced (62%) fill factor. The performances of these devices are compared with standard n-on-p technology. The inversion of the junction results in a remarkable improvement of PDE in blue wavelength range. Moreover all the tested devices show very good single photoelectron resolution also for high overvoltage values confirming the excellent single photon detection capability of SiPM technology. In this work a comprehensive SiPM model integrating the electrical and statistical behavior of the device is also presented. We used a Monte Carlo model for statistical and a SPICE circuit model for the electrical behavior description of the SiPM.
We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon
photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively.
Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of
nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm).
For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset
overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower
overvoltages, while a shrink is observed when the reverse bias voltage increases. With regards to our responsivity
measurements, carried out in the abovementioned spectral range, we have found a peak around 669 nm for the N-on-P
and a peak at 417 nm for the P-on-N SiPM. A physical explanation of the all experimental results is also provided in the
We electrically and optically tested both single pixels and complete arrays of Silicon Photomultipliers, from 5×5 to
64x64, fabricated by STMicroelectronics. Single cell devices operation was studied as a function of the temperature from
-25°C to 65°C varying the voltage over breakdown, from 5% up to 20% of the breakdown voltage. Optical
characterization was performed using a laser at 659 nm and opportunely chosen filters to vary the optical power. We
determined the single pixel gain by using both the time resolved dark count signal and the current under controlled
illumination. Typical gain values above 1×105 and above were obtained for operation times of 10 ns, while higher gains
are obtained for longer integration times and lower photon flux.
Single photon Si detectors were fabricated by STMicroelectronics and fully characterized in standard operation
conditions and after irradiations. Both single cells and arrays, of dimensions ranging from 5x5 up to 64x64, were
electrically tested. The devices operation was studied as a function of the temperature from -25°C to 65°C varying the
voltage over breakdown, from 5% up to 20% of the breakdown voltage before and after irradiation using both light ions,
10 MeV B ions to doses in the range 3×107 - 5×1010 cm-2, and X-rays irradiations in the range 0.5 - 20 krad(Si). Optical
characterization was performed using a laser at 659 nm and opportunely chosen filters to vary the optical power. A
strong difference in the radiation damage effect is observed for the two different irradiation sources. Ion irradiation, or
better implantation, produces a damage preferentially sitting in the active device region, hence even at the lowest
irradiation dose the device functionality is compromised, while at the highest dose the device is completely blind. On the
other hand, X-rays produce damage in a low concentration, in fact it does not significantly affect the device dark current,
only an increase in the leakage current under breakdown is observed. Hence the device functionality is preserved to
doses up to 20 Krad(Si).
Today, single photon imaging represents one of the most challenging goals in the field of photonics. Many areas are
involved: nuclear and particle physics, astronomy, and, in the biophysics field, the newest technique to investigate the
state of several biological systems by detecting the ultra-weak luminescence emitted from the excited sample under
study. Aim of the work is the realization of a single photon imaging device able to identify the position and the arrival
time of the impinging photons from ultra low intensity sources. The main features of a 2-D array of Single Photon
Avalanche Diodes, manufactured by ST-Microelectronics, are shown.
In this contribution we present the results of the first morphological and electro-optical characterization of Silicon
Photomultipliers (SiPM) for nuclear medical imaging applications fabricated in standard silicon planar technology at the
STMicroelectronics Catania R&D clean room facility. We have improved our previous Geiger Mode Avalanche
Photodiodes (GMAP) technology in order to realize a photodetector with relevant features in terms of single-photoelectron
resolution, timing and photon detection efficiency. The performances of our devices, investigated in
several experimental conditions and here reported make ST-SiPM suitable in many applications like for example PET
(Positron Emission Tomography).
Design and characterization of a new generation of single photon avalanche diodes (SPAD) array, manufactured by STMicroelectronics
in Catania, Italy, are presented. Device performances, investigated in several experimental conditions
and here reported, demonstrate their suitability in many applications. SPADs are thin p-n junctions operating above the
breakdown condition in Geiger mode at low voltage. In this regime a single charged carrier injected into the depleted
layer can trigger a self-sustaining avalanche, originating a detectable signal. Dark counting rate at room temperature is
down to 10 s-1 for devices with an active area of 10 μm in diameter, and 103 s-1 for those of 50 &mgr;m. SPAD quantum
efficiency, measured in the range 350÷1050 nm, can be comparable to that of a typical silicon based detector and reaches
the values of about 50% at 550 nm for bigger samples. Finally, the low production costs and the possibility of integrating
are other favorable features in sight of highly dense integrated 1-D or 2-D arrays.
SINPHOS is a monolithic micro-device, able to measure simultaneously time distribution and spectrum of photons coming from a weak source like Delayed Luminescence of biological systems. In order to achieve this challenging goal, we use: Deep Lithography with Ions (DLI) and microelectronic technologies for the fabrication of dedicated passive micro-optical elements and for the realization of Single Photon Avalanche Diode (SPAD) detectors, respectively
In this paper we report the results relative to the design and fabrication of Single Photon Avalanche Detectors (SPAD) operating at low voltage in planar technology. These silicon sensors consist of pn junctions that are able to remain quiescent above the breakdown voltage until a photon is absorbed in the depletion volume. This event is detected through an avalanche current pulse.
Device design and critical issues in the technology are discussed.
Experimental test procedures are then described for dark-counting rate, afterpulsing probability, photon timing resolution, quantum detection efficiency. Through these experimental setups we have measured the electrical and optical performances of different SPAD technology generations. The results from these measurements indicate that in order to obtain low-noise detectors it is necessary to introduce a local gettering process and to realize the diode cathode through in situ doped polysilicon deposition. With such technology low noise detectors with dark counting rates at room temperature down to 10c/s for devices with 10mm diameter, down to 1kc/s for 50mm diameter have been obtained.
Noticeable results have been obtained also as far as time jitter and quantum detection efficiency are concerned.
This technology is suitable for monolithic integration of SPAD detectors and associated circuits. Small arrays have already been designed and fabricated. Preliminary results indicate that good dark count rate uniformity over the different array pixels has already been obtained.